Right, but compilation performance is not a race in which you have to be first, but a minimum threshold that you must meet. Compilation just has to be fast enough that it doesn't annoy developers most of the time. Once you achieve that they'll mostly stop complaining. I believe Clang et al are fast enough.
(This is true for performance and optimisation is general: fast enough is good enough.)
(This is true for performance and optimisation is general: fast enough is good enough.)